In a motor vehicle, power from a power source such as an engine is transferred through a drivetrain to wheels to provide movement of the vehicle. The wheels are either of the driven or non-driven type and are operably connected to a steering system of the motor vehicle through a wheel bearing as is known in the art. Wheel bearings, of the type in which an inner race or spindle is supported within a surrounding outer race or hub by two axially spaced rows of rolling elements, such as bearing balls, are frequently utilized for motor vehicles.
An example of a wheel bearing is disclosed in commonly assigned U.S. Pat. No. 4,179,167 which issued Dec. 18, 1979. A separable race slides freely onto an outer surface of a spindle until it hits an outer ball row. As it makes contact with the outer ball row, its outer edge rests past an inner wall of a groove machined into the spindle. The separable race is forced and held against its ball row by an assembly apparatus to a desired preload, and then the axial spacing of its outer edge from an outer wall of the groove is accurately gauged. Next, a pair of selected thickness keeper rings, chosen from a pre-machined assortment, are tightly inserted between the outer edge of the separable race and a far wall of the groove. The keeper rings hold the proper race location and so maintain the preload or end play as desired. Finally, a sleeve shaped retaining ring must be swaged over the keeper rings to hold them radially down into the groove.
Another example of a wheel bearing is disclosed in U.S. Pat. No. 3,589,747 which issued Jun. 29, 1971. The wheel bearing includes a cylindrical body having an out-turned flange on one axial end and inner race ring bearing surfaces formed by grinding an exterior surface of a forward end of the body. The wheel bearing includes a one-piece common outer race ring overlying the inner race ring bearing surfaces and at least two rows of rolling elements. The outer race ring is held in position by cold-forming the body to form a locking flange for retaining the outer race ring in place.
While these wheel bearings have worked well over the years, several refinements have been made to the overall design. More recently, a method for retaining a separable bearing race to an inner bearing member was disclosed in a commonly assigned pending U.S. patent application Ser. No. 723,452, filed Oct. 7, 1996 entitled "Bearing With Integrally Retained Separable Race", the disclosure of which is hereby incorporated by reference. In this example, a deformable lip of the inner bearing member is rolled over into a race abutting bead which prevents movement of the inner bearing member.
Modern vehicle systems, such as anti-lock braking, navigational, traction control and tire pressure monitoring rely on wheel speed as an input. The incorporation of a rotational sensor in a vehicle wheel bearing is an indicator of wheel rotation from which wheel speed can be computed.
A commonly known sensing mechanism of wheel rotation is a variable reluctance sensor for sensing the rotational speed of a toothed target, also referred to as a sensor ring. Such a sensor is disclosed in commonly assigned U.S. Pat. No. 5,606,254 which issued Feb. 25, 1997. The sensor includes an elongated core interposed between two permanent magnets which generate additive magnetic flux passing longitudinally through the elongated core. The elongated core and permanent magnets are encircled by a multi-turn electrical coil, which is wound transversely about a longitudinal dimension. A portion of the elongated core and permanent magnets extends beyond the electrical coil and are positioned adjacent a periphery of the sensor ring and define an air gap between them. In this example, the sensor ring is mounted to the wheel bearing. In operation, as the sensor ring rotates, the air gap is varied which, in turn, varies the magnitude of the opposing longitudinal components of magnetic flux with respect to one another. The resulting output voltage generated in the electrical coil has an amplitude proportional to the rate of change of the net longitudinal flux magnitude and a frequency proportional to the rotational speed of the sensor ring.
In the past, the sensor ring was installed by first orienting it, and pressing it onto the inner ring portion of the wheel bearing. While this assembly method has proven to be solid and robust for many years, a less costly system in terms of parts, assembly steps or configuration is desired.